Conventionally known physical quantity sensor apparatuses are, for example, a physical quantity sensor apparatus which corrects the output characteristics of a physical quantity sensor element, by converting an analog signal output from the physical quantity sensor element to a digital signal by an A/D converter (ADC: Analog-to-Digital Converter) and carrying out computational processing using a computation circuit such as a CPU (Central Processing Unit) and a DSP (Digital Signal Processor).
An apparatus that has been proposed as a physical quantity sensor apparatus of this kind is one provided with: an analog input unit which converts an analog input signal input from a control object, into a digital signal and outputs the digital signal; a temperature detector which detects an ambient temperature at the periphery of the apparatus; a temperature correction table which is created on the basis of actual measurement of the error between the digital value of the digital signal and the expected value of an analog input signal, under different temperature conditions and stores correction data in which the ambient temperature and a correction value are associated on a one-to-one basis; and temperature correction means for reading a correction value corresponding to the temperature detected by the temperature detector and correcting the digital value read from the analog input circuit by this correction value to obtain final digital data (see, for example, Patent Document 1 below).
Furthermore, in another proposed apparatus, an analog signal from a semiconductor pressure converter which changes in accordance with a measured pressure is converted into sequential digital uncompensated pressure data by a first A/D converter, in addition to which an analog signal which changes in accordance with the measured temperature output from a temperature sensing element is converted into sequential digital uncompensated temperature data by a second A/D converter, and when this respective data is supplied to a computing apparatus, the computing apparatus reads out, from a storage unit, temperature data for compensation at least two reference temperatures in an operating pressure range and temperature range stored in the storage unit, and pressure data for compensation at least two reference pressures at each reference temperature stored in the storage unit (see, for example, Patent Document 2 below).
Moreover, another proposed apparatus is provided with: a pressure sensor circuit which generates a voltage level detection signal corresponding to a detected pressure; a temperature detection circuit which generates a temperature signal having a voltage level corresponding to the temperature of the pressure sensor circuit; a reference voltage generating circuit which generates a reference signal having a uniform voltage level, regardless of the detected pressure and temperature of the pressure sensor circuit; an A/D converter circuit for converting the detection signal, the temperature signal and the reference signal into digital data; an analog multiplexer which selectively passes the detection signal, the temperature signal and the reference signal and supplies same as a conversion object signal to the A/D conversion circuit; and signal processing means for calculating an applied pressure P by carrying out a computing process P={(T/A−b)×(−e/a)+D/A−f}/{(T/A−b)×c/a+d}, when the applied pressure at the pressure sensor circuit is P, the digital data converted by the A/D converter circuit respectively from the detection signal, the temperature signal and the reference signal are pressure information D, temperature information T and reference information A, the temperature coefficient of the sensitivity of the pressure sensor circuit is c, the room temperature sensitivity of the pressure sensor circuit is d, the temperature coefficient of the offset of the pressure detection value is e, the room temperature offset value of the pressure detection value is f, the temperature coefficient of the temperature detection value is a, and the room temperature offset value of the temperature detection value is b; wherein the analog multiplexer is composed so as to pass the reference signal and the temperature signal prior to the detection signal, and the signal processing means carries out a computing process based on the reference information A and the temperature information T corresponding to the reference signal and the temperature signal, and then carries out a computing process based on the results of this computing process and the pressure information D corresponding to the detection signal, thereby calculating the applied pressure P (see, for example, Patent Document 3 below).
Patent Document 1: Japanese Patent Application Publication No. 2009-260626
Patent Document 2: Japanese Patent Application Publication No. H6-265424
Patent Document 3: Japanese Patent Application Publication No. H10-339673